Source Area Treatment of a TCE Plume by Coated Microbubble Ozone and Sequential ERD at a Portland, Oregon, Facility

摘要

The PECO site is a machine shop and die-casting facility which has operated since the 1930s. Trichloroethene (TCE) was used as a degreaser at the facility's west plant building from the 1950s until 1995. A TCE plume was observed beneath the west plant building, extending in a southwesterly direction towards the nearby Willamette River. TCE plume concentrations ranged from >100,000 ug/L in a localized hotspot beneath the source area to 1,000 ug/L at the downgradient property boundary. The vertical extent of the plume was greatest below the source area, where DNAPL was suspected within the uppermost 10 feet of the water table aquifer. The groundwater gradient varied from 0.015 to 0.031 ft. per ft. horizontally, depending on the aquifer zone. The formation consisted of heterogeneous gravel with zones of relatively low permeability. TCE source reduction using a carbonate ISCO product had been attempted previously at the site, however, problems in distributing the oxidant material through the saturated zone severely limited the treatment's effectiveness. After review of alternatives and pilot testing, full-scale Perozone? implementation began in October 2008 (Ecker and McBeth, 2010).